Re: [PATCH v2 02/14] scsi: assert that callbacks run in the correct AioContext

[Kevin Wolf]

Am 05.12.2023 um 19:19 hat Stefan Hajnoczi geschrieben:
> Since the removal of AioContext locking, the correctness of the code
> relies on running requests from a single AioContext at any given time.
> 
> Add assertions that verify that callbacks are invoked in the correct
> AioContext.
> 
> Signed-off-by: Stefan Hajnoczi 

Reviewed-by: Kevin Wolf 

[PATCH v2 02/14] scsi: assert that callbacks run in the correct AioContext

[Stefan Hajnoczi]

Since the removal of AioContext locking, the correctness of the code
relies on running requests from a single AioContext at any given time.

Add assertions that verify that callbacks are invoked in the correct
AioContext.

Signed-off-by: Stefan Hajnoczi 
---
 hw/scsi/scsi-disk.c  | 14 ++
 system/dma-helpers.c |  3 +++
 2 files changed, 17 insertions(+)

diff --git a/hw/scsi/scsi-disk.c b/hw/scsi/scsi-disk.c
index 2c1bbb3530..a5048e0aaf 100644
--- a/hw/scsi/scsi-disk.c
+++ b/hw/scsi/scsi-disk.c
@@ -273,6 +273,10 @@ static void scsi_aio_complete(void *opaque, int ret)
 SCSIDiskReq *r = (SCSIDiskReq *)opaque;
 SCSIDiskState *s = DO_UPCAST(SCSIDiskState, qdev, r->req.dev);
 
+/* The request must only run in the BlockBackend's AioContext */
+assert(blk_get_aio_context(s->qdev.conf.blk) ==
+   qemu_get_current_aio_context());
+
 assert(r->req.aiocb != NULL);
 r->req.aiocb = NULL;
 
@@ -370,8 +374,13 @@ static void scsi_dma_complete(void *opaque, int ret)
 
 static void scsi_read_complete_noio(SCSIDiskReq *r, int ret)
 {
+SCSIDiskState *s = DO_UPCAST(SCSIDiskState, qdev, r->req.dev);
 uint32_t n;
 
+/* The request must only run in the BlockBackend's AioContext */
+assert(blk_get_aio_context(s->qdev.conf.blk) ==
+   qemu_get_current_aio_context());
+
 assert(r->req.aiocb == NULL);
 if (scsi_disk_req_check_error(r, ret, false)) {
 goto done;
@@ -496,8 +505,13 @@ static void scsi_read_data(SCSIRequest *req)
 
 static void scsi_write_complete_noio(SCSIDiskReq *r, int ret)
 {
+SCSIDiskState *s = DO_UPCAST(SCSIDiskState, qdev, r->req.dev);
 uint32_t n;
 
+/* The request must only run in the BlockBackend's AioContext */
+assert(blk_get_aio_context(s->qdev.conf.blk) ==
+   qemu_get_current_aio_context());
+
 assert (r->req.aiocb == NULL);
 if (scsi_disk_req_check_error(r, ret, false)) {
 goto done;
diff --git a/system/dma-helpers.c b/system/dma-helpers.c
index 528117f256..9b221cf94e 100644
--- a/system/dma-helpers.c
+++ b/system/dma-helpers.c
@@ -119,6 +119,9 @@ static void dma_blk_cb(void *opaque, int ret)
 
 trace_dma_blk_cb(dbs, ret);
 
+/* DMAAIOCB is not thread-safe and must be accessed only from dbs->ctx */
+assert(ctx == qemu_get_current_aio_context());
+
 dbs->acb = NULL;
 dbs->offset += dbs->iov.size;
 
-- 
2.43.0